The present invention relates to apparatus for selectively viewing information from a plurality of recording elements. More specifically, the invention relates to such apparatus having particular utility with interchangeable sets of photographic units which include a circular information-bearing strip interrupted by a notched-out portion or open sector.
The prior art can be classified into numerous categories of viewing devices, including various types of projectors for presenting images on a screen, video players for displaying information through television receivers, and viewers for inspecting recording elements directly. Typical examples are disclosed in U.S. Pat. Nos. 3,146,666, 3,276,314, 3,778,545, and 2,511,334. Certain of the prior art devices, most noteably relating to photocomposing machines, are specifically adapted for selectively viewing information from a plurality of character disks. Examples of this type are disclosed in U.S. Pat. Nos. 2,767,628; 3,099,945; 3,339,470; 3,791,271; and 3,959,801. Of particular interest is U.S. Pat. No. 2,989,904, which discloses a photo-type composing machine for selectively projecting images from a plurality of character disks having circular strips of information interrupted by an open sector. As there disclosed, the character disks are accumulated on an axis of rotation, defined by a spindle, with their open sectors aligned apparently to facilitate axial indexing of the disks relative to the viewing optics. Rotational indexing of the selected disk provides for viewing particular information on that disk.
While prior art devices, such as those mentioned above, appear to be satisfactory for their intended purposes, previous teachings have not offered solutions to the many difficult problems that arise when interchangeable sets of accumulated photographic disks are to be viewed, for example, in a consumer environment. Convenient handling of the disks while they are removed from the apparatus is a typical problem. Others relate to interchanging the sets, i.e., the loading and unloading of the apparatus, and the requirements of convenient, reliable operation at a reasonable cost for the consumer. Until these and similar problems are solved, the advantages of such apparatus, even though available in sophisticated equipment to skilled users, will not be accessible to the consumer.
The above and other problems that are alleviated by the present invention will become more apparent from an examination of the prior art in connection with the following description.